are dwindling faster than anyone thought, putting nearly a billion people living in South Asia in peril of losing their water supply.

Throughout India, China, and Nepal, some 15,000 glaciers speckle the Tibetan Plateau. There, perched in thin, frigid air up to 7200 metres above sea level, the ice might seem secluded from the effects of global warming.

But when the team analysed samples of glacier, what they found stunned them.

Radioactive signals

Glaciers can be dated by looking for traces of radioactivity buried in the ice. These are the leftovers from US and Soviet atomic bomb testing in the 1950s and 1960s.

In the Naimona'nyi samples, there was no sign of the tests. In fact, the glacier had melted so much that the exposed surface of the glacier dated to 1944.

"We were very surprised not to find the 1962-1963 horizon, and even more surprised not to find the 1951-1952 signal," says Thompson.

In more than twenty years of sampling glaciers all over the world, this was the first time both markers were missing.

He suspects the reason for this is that high-altitude glaciers, despite residing in colder temperatures, are more sensitive to climate change.

As more heat is trapped in the atmosphere, he said, it holds more water vapour. And when the water vapour rises to high altitudes it condenses, releasing the heat into the upper atmosphere, where high mountain landscapes feel the brunt of warming.

"At the highest elevations, we're seeing something like an average of 0.3°C warming per decade," says Thompson. "The Intergovernmental Panel on Climate Change projects 3°C of warming by 2100. But that's at the surface; up at the elevations where these glaciers are there could be almost twice as much, almost 6°C."

"I have not seen much as compelling as this to demonstrate how some glaciers are just being decapitated," says Associate Professor Shawn Marshall of the University of Calgary.

Marshall, who studies glaciers in North America, says it's striking how much worse glaciers near the equator are than those in the Canadian Rocky and Cascade mountain ranges.